Tympan



March 6, 1951 w, PAGE 2,544,279

'I'YMPAN Filed July 28, 1948 2 Sheets-Sheet 1 W INVENTOR.

March 6, 1951 w, PAGE 2,544,279

max m Filed July 2a, 1948 2 Sheets-Sheet 2 I00, 00. cp

5/15/12 LOAD -6'/?AM5 IN 'ENTOR.

mi: 42M JM c 1 Patented Mar. 6, 1951 TYMPAN William Page, Appleton, Wia,assignmto Swlgart Paper 00., Chicago, 111., a corporation of IllinoisApplication July 28, 1948, Serial No. 41,070

This invention relates to tympan paper used in printing apparatus andmore particularly to the laminated type of tympan disclosed in UnitedStates Patent No. 1,487,158 granted March 18, 1924, to George W. Gould.

In the operation of printing presses, one of the important problems isthe maintenance of a uniform impression pressure between all points ofthe type and the surface being printed. This pressure is extremelycritical, especially in certain types of printing. and a variation ofonethousandth of an inch will produce blurring, or fading and arejection of the work. However, to minimize wear of the type acushioning action is necessary and it is essential that such cushioningaction be also maintained if the uniform impression pressure is to bemaintained. Packing and a protecting tympan therefor are accordinglyused about the impression roller. However, to serve its purpose thetympan should be of uniform thickness to assure uniform impressionpressure, it should have a high strength against tearing and a hardouter surface, and it should be resilientto protect the type againstexcessive wear due to the repeated pounding by thetype as the printingimpressions are made. The repeated pounding by the type tends moreoverto destroy in a short time the resilience of the tympan and then thetympan itself. It was found that in the type of tympan disclosed in theaforesaid patent the parchment would separate from the kraft or undersheet after several hundred thousand impressions as the result of theresilience being destroyed by a breakdown of the glue or paste betweenthese layers. Failure of a tympan to have a life in excess of severalhundred thousand impressions is costly because the press must be shutdown each time the tympan must be replaced and the packing and typereadjusted each time to secure the uniform impression pressure betweenthe type and impression roller.

6 Claima. (CL Hi -54.5)

2 bined. by an adhesive or paste capable of maintaining its bondingaction under repeated pounding of the type.

A further object of the invention is'to provide in a tympan of thischaracter an adhesive or paste that will maintain a firm backing for theparchment and will prevent a separation of the parchment from the underlayer as well as provide the" desired resilience for the tympan.

A still further object of the invention is to provide, in connectionwith this type of tympan. an adhesive of a composition preferablyemploying a starch paste having a predetermined viscosity and an aqueousemulsion of a resin. It is found that the proper preparation of thestarch paste and its viscosity are quite essential to the character ofthe adhesive, after the emulsion of resin is added, to produce a tympanof the long life desired.

Other objects and advantages of the invention will be apparent from thefollowing detail description when taken in connection with theaccompanying drawings, in which:

Figure 1 is a diagrammatic sectional view illustrating a form of pressemploying a tympan sheet embodying the invention;

Fig. 2 is an enlarged perspective view of the tympan sheet, a portionbeing broken away to show the two layers thereof and the adhesivetherebetween;

Fig. 3 illustrates diagrammatically a preferred method of making thistympan sheet;

Fig. 4 is an exaggerated section of a portion of an impression cylinderto show the packing and make-up below the tympan paper; and I Fig. 5 isa chart showing a flow curve to be referred to in determining the flowproperties of the adhesive at the time they aqueous emulsion ofcellulose acetate is added.

An object of the invention is to provide an improved form of tympan ofthe type disclosed in the aforesaid patent that is of uniform thickness,high tear strength, hard outer surface and a resilience that willpersist and not be destroyed by the pounding of the type throughout acontinuous printing operation greatly exceeding anything heretoforeexperienced and running as high as five million impressions without achange.

Specifically the invention is directed to a combination of an undersheet orlayer of hightensile strength and an outer layer having a hardsurface such as parchment, these layers being com- In the usual rotarypress, the sheet of paper i being printed passes between an impressioncylinder 2 and printing cylinder 3 which prints upon one side of thesheet, and then passes between a printing cylinder 4 and an impressioncylinder 5 which prints upon the other side of the sheet L The side ofthe sheet of paper I being printed by the printing cylinder 3 must beprotected against impairment as it passes over impression cylinder 5. Tothis end, a laminated tympan sheet 8 covers the peripheral surface ofthe cylinder 5, which sheet may be secured thereto in themannerdisclosed in the aforesaid patent or in any suitable way.

Tympan sheet 8 preferably comprises a sheet 9 of material possessingrelatively great tensile strength and a sheet In of parchment paper.Preferably sheet 9 may be rope paper, kraft paper or jute, or' otherpaper possessing-considerable tensile strength. Both sheets 9 and II]are then firmly bonded together by an adhesive .which I shall nowdescribe.

The adhesive is preferably a composition embodying a starch paste towhich an emulsion of a resin is added, the starch paste beingcharacterized by a predetermined viscosity at the time the emulsion ofresin is added in Order to obtain the desired new result. Thepreparation of the starch paste should be conducted under controlledconditions in order that the starch paste will have said predeterminedflow property or predetermined viscosity'at the time the emulsion ofresin is added. a I

It is found that this flow property or viscosity may be obtained whenthe following is adopted: First, mix dry a suitable amount of starch,say corn or tapioca starch, with a suitable amount of diastase enzyme.the mixture to a uniform consistency and hold until the enzymes convertthe starch to a form which produces a paste of low viscosity. In thisstep, the temperature and holding period are factors determining theviscosity of the paste which will be obtained. It is also found that theaddition of a suitable preservative such as pentachlorphenol preventsbacterial growth by the enzymes during the conversion period. As soon asthe conversion has taken place, the temperature may be raisedsufliciently to destroy the enzymes.

Specifically, to every 100 lbs. of corn starch approximately 4 oz. ofdiastase enzyme such as Diastase BB may be used, and, after well mixeddry, 138 lbs. of water at 75 C. may be added to the mixture. Thetemperature of the water may vary between 60 C. and 78 C., but themixture, after kneaded to a uniform consistency, is heated to 75 C. andheld at this temperature for, say. 30 minutes when the preservative, tothe extent of 1% on the basis of the dry starch used, is added. Afterthis preservative is added to prevent bacterial growth, the mixture isheated to 93 C. or slightly above to destroy the enzymes and, of course,stop further conversion. It is then cooled to a temperature ofapproximately 38 C.

When the starch paste is treated in the above manner, it should have aviscosity range permitting the mixture to receive an aqueous emulsion ofa resin combined with triethanolamine and a thinner suchas water. Thetriethanolamine is a coagulant inhibitor and may be omitted ifcoagulation does not occur. It is found that the adhesive combining theparchment and kraft will produce a tympan paper giving the desiredresult when starch paste has this viscosity range at the time the resinand triethanolamine are added. For 100 lbs. of starch initially treatedas above described, it is desirable first to take 50 lbs. of an aqueousemulsion of a resin obtainable in a form commercially known asGin-Bond," which is composed of approximately 35% of cellulose acetate,16% of butyl carbitol and 48% of water, the cellulose acetate being madestable by combining it with the butyl carbitol and a fractional per centof mineral or saponifiable oil, and then stirring the same if desired in/g 1b. of triethanolamine dissolved in lbs. of water as a thinner. Thecombined aqueous emulsion resin and triethanolamine is then mixed withthe starch paste to produce the adhesive Then add water and knead.

designated ll combining the parchment l0 and the kraft 9. o

g If the viscosity of the starch paste after the first cock is not'inthe correct range, additional unconverted starch may be added before theinclusion of the aqueous emulsion of resin and the triethanolamine. Theviscosity may be measured prior to the cooling step and after theconversion has been checked. While the starch paste is still at, say, 75C., portions may be tested at different shear loads with a Stormer typeviscometer and the results compared with the graph or chart shown inFig. 5. A flow curve may be plotted, and, if this cure intersects at orbelow the 10% range indicated on the chart in Fig. 5, the viscosityrange is within proper limits and satisfactory to receive the aqueousemulsion of resin and the triethanolamine. If the flow curve intersectsabove the 10% range, the viscosity of the batch must be corrected byadding dry starch to the first cook in an amount equal in percentage tothe pounds of wet paste made. For example, if 100 lbs. of wet paste ismade and the flow curve intersects the curve illustrated on the chartshown in Fig. 5 at the range indicated by 25%, then 25 lbs. of drystarch should be added to the first cook, but without a further cookingstep. The curve shown in Fig. 5 is empirical in character in that it hasbeen arbitrarily formed by trial method. The abscissa values are interms of shear loads in grams and the ordinate values are in terms of1/t where t is the number of seconds per 100 revolutions of the Stormertype of viscometer. Any other viscometer may be used if it is of theshear type.

However, with the Stormer type of viscometer used in the preparation ofthe chart, it has been determined that the point designated 0%represents a viscosity of 15,723 centipoises. while the point designatedas 10% represents a viscosity of 8,755 centipoises. The viscosity in therange below the zero mark will increase to approximately 97,800centipoises as indicated in Fig. 5. Consequently, the viscosity rangefor the starch at the time the aqueous emulsion resin is added, isbetween 8,755 to 100,000 centipoises. Outside-of this range, acorrection is desirable and the above chart may be conveniently used toeffect such correction. If the chart is not used, the viscosity of thestarch may be measured in any known way in terms of centipoises orequivalent units of measurement.

Other resins as ethyl cellulose, acrylic and vinyl resins, etc., mayalso be used.

To prevent ink from gathering upon the outer surface of the tympanpaper, a felted roller 12 is usually positioned below impressioncylinder 5, as shown in Fig. 1, to contact this outer surface andthereby wash the same with any suitable ink solvent.

Fig. 4 illustrates diagrammatically in cross section a typicalimpression cylinder with its packing designated I4 and its make-up as[5. Makeup l5 usually comprises a plurality of thin layers of paper thatcompensate for any unequal pressure between the type and plates and theimpression cylinder so that each impression will be made with a uniformpressure throughout if the tympan is of uniform thickness and a properadjustment of the type is made. The slightest variation is detrimentalto good work and often a pressman will labor for hours to secureequalization. During this period the press remains idle, which is costlyand very undesirable.

I find that the adhesive ll between the parchment Hi and the sheet 9maintains a firm but resilient backing for parchment sheet In andprotects packing l4 and make-up l5 so that as many as several millionimpressions may be now made compared to the several hundred thousandimpressions as heretofore by the tympan paper disclosed in the aforesaidpatent. Not only may this greater number of impressions be now madewithout replacement of the tympan, but the press may operatecontinuously without requiring shutdowns to rebuild the make-up oradjust the type before a run is completed.

I propose to apply the adhesive ll uniformly to the inside surface ofboth sheets 9 and I0. As illustrated in Fig. 3, sheets 9 and I0 may befed over roler l6 so that these sheets pass rotating brushes I! thatwipe a thin layer of the adhesive thereon at substantially the same timeso that the time interval these sheets carry the adhesive in wet form isthe same before they are pressed firmly together by passing betweenpress rolls I8. It wi'l be understood that this adhesive ll may beapplied uniformly in other ways.

Without further elaboration, the foregoing will so fully explain thegist of my inventionthat others may, by applying current knowledge,readily adapt thesame for use under varying conditions of service,without eliminating certain features, which may properly be said toconstitute the essential items of novelty involved, which items areintended to be defined and secured to me by the following claims.

I claim:

1. A washable tympan for printing presses consisting of a laminatedsheet made up of a sheet of paper possessing relatively great tensilestrength and a sheet of parchment paper forming the exposed surface ofthe tympan, and an adhesive between the two sheets consisting of astarch paste of a predetermined viscosity and an aqueous emulsion ofcellulose acetate resin.

2. A washable tympan for printing presses consisting of a laminatedsheet made up of a sheet of paper possessing relatively great tensilestrength and a sheet of parchment paper forming the exposed surface ofthe tympan, and an adhesive between the two sheets consisting of anenzyme treated starch paste having a predetermined viscosity and anadded cellulose acetate resin emulsion.

v3. A washable tympan for printing presses consisting of a laminatedsheet made up of a sheet of paper possessing relatively great tensilestrength and a sheet of parchment paper forming the exposed'surface ofthe tympan, and an adhesive between the two sheets consisting of aconverted starch paste having a viscosity in a range between 8,755centipoises and 100,000 centipoises and a resin emulsion.

4. A washable tympan for printing presses consisting of a laminatedsheet made up of a sheet of paper possessing relatively great tensilestrength and a sheet of parchment paper forming the exposed surface ofthe tympan, and an adhesive between the two sheets consisting of astarch paste of a viscosity in a range between 8,755 centipoises and100,000 centipoises and a mixture of an aqueous emulsion of resin and acoagulant inhibitor.

5. In a tympan for printing presses consisting of a sheet of relativelygreat tensile strength and a sheet of parchment forming a hard exposedsurface of thetympan, an adhesive between the two sheets comprisingenzyme converted starch substantially in the ratio of parts of starchand 138 parts of water and approximately 50 parts of a resin emulsionwherein the resin comprises in the neighborhood of 35% of the emulsion.

6. In a tympan for printing presses consisting of a sheet of relativelygreat tensile strength and a sheet forming a hard exposed surface of thetympan; an adhesive between the two sheets comprising a starch paste. ofa viscosity between 8,755 centipoises and 100,000 centipoises mixed witha resin emulsion.

WILLIAM PAGE.

REFERENCES CITED The following references are of record in the flle ofthis patent:

UNITED STATES PATENTS Kesler et al. Apr. 5, 1949

4. A WASHABLE TYMPAN FOR PRINTING PRESSES CONSISTING OF A LAMINATEDSHEET MADE UP OF A SHEET OF PAPER POSSESSING RELATIVELY GREAT TENSILESTRENGTH AND A SHEET OF PARCHMENT PAPER FORMING THE EXPOSED SURFACR OFTHE TYMPAN, AND AN ADHESIVE BETWEEN THE TWO SHEETS CONSISTING OF ASTARCH PASTE OF A VISCOSITY IN A RANGE BETWEEN 8.755 CENTIPOISES AND100,000 CENTIPOSES AND A MIXTURE OF AN AQUEOUS EMULSION OF RESIN AND ACOAGULANT INHIBITOR.